The present embodiments relate to a compression plate for tomosynthesis images using an x-ray device configured to take tomosynthesis images.
X-ray devices are widely used in medical diagnosis. In some cases, devices for x-ray diagnosis are specifically embodied for particular examinations in order to take account of the particular requirements during the examination. One example of a specific diagnostic device is the mammography device for the examination of breast tissue in patients. To enhance the quality of the images acquired, the breast to be examined is compressed with the aid of a compression plate. During a mammography examination, x-rays are emitted by an x-ray source, penetrate the compressed breast and are subsequently detected by a detector.
Conventional examinations using mammography may include a single image or two images acquired from different angles (e.g., mediolateral oblique (MLO) and cranio-caudal (CC) acquisition). With this type of imaging, the attenuation of the x-rays on penetration of the tissue is detected. The attenuation is dependent on the density of the penetrated tissue. On account of the changed density of diseased tissue, diseased tissue may be diagnosed from the acquired images. An important limitation of this process lies in the fact that information about a three-dimensional object (e.g., breast tissue) is obtained by a detector with a resolution in two dimensions. In the direction of the x-ray beam (e.g., perpendicular to the detector surface) only general information (e.g., overall attenuation) is obtained (e.g., practically no resolution exists). This limitation may lead to misdiagnoses.
Tomosynthesis is a development of conventional mammography that allows a resolution orthogonal to the detector surface. During the course of tomosynthesis, the x-ray source follows a trajectory (e.g., an arc of e.g. 50°). On passage through the trajectory, images are acquired from different angles (e.g., 10-50 images). A three-dimensional image of the object under examination may be obtained or reconstructed from this plurality of images by reconstruction algorithms. The three-dimensional image makes better diagnosis and localization of diseased tissue possible.
Components of the mammography device are to be adapted for tomoacquisition. For example, specific requirements are produced for the compression plates used in the imaging. For example, US 2006/0262899 A1 discusses adaptations of a compression paddle with respect to tomoacquisition (e.g., embodiment of the paddle for preventing shadows at the edges).
The general situation for acquiring tomosynthesis images is shown in FIG. 2. Disposed on a holder 3 are an object table 1 (e.g., containing the detector) and a compression plate 2, using which the breast 11 to be examined is compressed. The x-ray source follows a trajectory 10, while the tomosynthesis images are being acquired. Positions 101, 102, 103 . . . are marked on the trajectory, for which an x-ray image is made in each case. These positions, for example, reflect the location of the focus of the x-ray source for these images. The spreading out of the x-ray beam is shown in the figure for three positions 101, 110 and 120. The shape of the x-ray beam is in most cases a fan or a cone. On account of the images being acquired from different angular positions, the compression plate 2 is to be wider than if only one central image (e.g., position 110) were made.